China has rich coal mine gas (coal bed gas) resource, and the occurrence of gas (coal bed gas) resource within the range of 2,000 m underground is approx. 30˜35 trillion m3. Effective exploitation and utilization of coal and gas resources is increasingly important in the development of national economy in China. Coal mine gas is a clean, efficient, and non-renewable energy source, with heat value as high as 33.5˜36.8 MJ/m3. The heat value of 1 m3 gas is equivalent to that of 1.3 kg standard coal. In addition, no harmful substance, such as nitrogen oxides and sulfides, etc., is produced in the utilization process of coal mine gas. More than 50% coal beds in China are coal beds with high gas content. In 2009, the total volume of coal mine gas released in the production in coal mines in China exceeds 15 billion m3. However, almost ⅔ coal mine gas is directly emitted into the atmosphere in the form of ventilation, causing severe waste of the precious energy resource and pollution to the atmospheric environment. Moreover, since the greenhouse effect of coal mine gas (coal bed gas) is 21 times of that of carbon dioxide, the resultant damage to the ozone layer is 7 times of that produced by CO2. At present, in the international carbon sequestration market, the carbon emission reduction can be sold for RMB85 Yuan per ton. An income of RMB 17 billion Yuan can be obtained per year due to the emission reduction and utilization of 15 billion m3 gas. Hence, by utilizing coal-mine gas (including ventilation gas) as a resource, not only direct economic benefits can be obtained in the aspect of gas utilization, but also rich returns can be obtained in the aspect of energy conservation and emission reduction.
At present, the low-concentration gas extracted from a coal mine is mainly used for electric power generation in an gas-internal combustion power generator set, but the concentration of the gas usually must be not lower than 6%; whereas low-concentration gas at 1%˜6% extracted from a coal mine usually is emitted directly. For treatment of the ventilation gas in a coal mine, available industrialization techniques include thermal countercurrent oxidation technique and catalyzed countercurrent oxidation technique. However, it is proved in field application that the surface heat dissipation and oxidation reaction on an oxidizing bed can be maintained stably by the heat release part of the gas oxidation reaction only if the concentration of the ventilation gas is higher than 0.5%. In addition, both the thermal countercurrent oxidation technique and the catalyzed countercurrent oxidation technique for treatment of ventilation gas utilize a heat storage oxidation principle in a “reciprocating flow mode”. With the gas flow reciprocating in the oxidation device, the temperature field in the device is always in a state of fluctuation, consequently, on one hand, the vapor parameters of the heat extracting device will fluctuate, and bring a severe impact on safe operation of the steam turbine set; on the other hand, the fluctuating temperature field in a reciprocating flow mode makes the regenerator always in a heat and cold alternating state, which also has a severe impact on the mechanical strength and service life of the regenerator.